Engineering topics
Beichman, C. A.
Publications and source records attributed to Beichman, C. A..
Nulling interferometry for extra-solar planet detection: sensitivity and image reconstruction
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Nulling interferometry for extra-solar planet detection: sensitivity and image reconstruction
This paper addresses the image reconstruction issues for nulling interferometer arrays and the sensitivities for planet detection.
NASA's terrestial planet finder: the search for (habitable) planets
One of the primary goals of NASA's Origins program is the search for hospitable planets. I will describe how the Terrestrial Planet Finder (TPF) will revolutionize our understanding of the origin and evolution of planetary systems, and possibly even find signs of life beyond Earth.
Discovery of Four Field Methane (T-type) Dwarfs with 2MASS
We report the discovery of four field methane (T-type) brown dwarfs using 2MASS survey data. One additional methane dwarf, previously discovered by SDSS, was also identified.
The Discovery of a Low Redshift, Red Quasar in the 2MASS Prototype Survey
The 2 Micron All Sky Survey (2MASS) will catalog over 100,000,000 individual objects, the vast majority of which will be stars of spectral type K and later. For many projects it will be important to develop techniques to identify interesting objects within this dataset.
Pushing the Limits: New Results from the ISO/IRAS Faint Galaxy Survey
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FIR-bright Galaxies with an Extreme [CII] Deficiency: Where are the PDRs?
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Infrared Surveys: A Golden Age of Exploration
This talk addresses the compelling scientific interest in the infrared and describes why, years from now, astronomers will view this decade as a golden era for the exploration of the infrared sky.
ISM Parameters in the Normal Galaxy NGC 5713
We report ISO Long Wavelength Spectrometer (LWS) observations fo the Sbc(s) pec galaxy NGC 5713. We have obtained strong detections of the fine-structure forbidden transitions [C(sub ii)] 158(micro)m, [O(sub i)]63(micro)m, and [O(sub iii)] 88(micro)m, and significant upper limits for[N(sub ii)]122(micro)m, [O(sub iii)] 52(micro)m, and [N(sub iii)] 57(micro)m. We also detect the galaxy's dust continuum emission between 43 and 197 microns.
The Mid-Infrared Color of NGC 6946
We analyze the new mid-infrared maps of NGC 6946 for variations in the color ratio fo the 7-to-15(micro)m emission. Our preliminary findings are that this mid-infrared color is remarkably constant between arms and inter-arm regions, and as a function of radius in the disk, excluding the nuclear region.
ISOCAM* Observations of NGC 6946: Mid-IR Structure
The nearby spiral galaxy NGC 6946 was observed with ISO-CAM in the mid-infrared, achieving 7inch resolution and sub-MJy sr(sup -1) sensitivity. Images taken with CAM filters LW2 (7(micro)m) and LW3 (15(micro)m) are analyzed to determine the morphology of this galaxy and understand beter the emission mechanisms.
The luminous starburst galaxy UGC 8387
We present broad-band J, H, and K images and K-band spectroscopy of the luminous starburst galaxy UGC 8387. The images show a disturbed morphology, tidal tails, and a single elognated nucleus. Near infrared color maps constructed from the images reveal that the nucleus region is highly reddened. Strong emission from the central 3 arcseconds in the 2.166 micrometer Brackett gamma, 2.122 micrometer H2 v = 1-0 S(1), and 2.058 micrometer He I lines is present in the K-band spectrum. From the Brackett gamma and published radio fluxes, we find an optical depth toward the nucleus of tau(sub V) approximately 24. The CO band heads produce strong absorption in the spectral region long-ward of 2.3 micrometers. We measure a 'raw' CO index of 0.17 +/- 0.02 mag, consistent with a population of K2 supergiants of K4 giants. The nuclear colors, however, are not consistent with an obscured population of evolved stars. Instead, the red colors are best explained by an obscured mixture of stellar and warm dust emission. The amount of dust emission predicted by the near-infrared colors exceeds that expected from comparisons to galactic H II regions. After correcting the spectrum of UGC 8387 for dust emission and extinction, we obtain a CO index of greater than or equal to 0.25 mag. This value suggests the stellar component of the 2.2 micrometer light is dominated by young supergiants. The infrared excess, L(sub IR)/L(sub Ly alpha) derived for UGC 8387 is lower than that observed in galactic H II regions and M82. This implies that either the lower or upper mass cutoff of the initial mass function must be higher than those of local star-forming regions and M82. The intense nuclear starburst in this galaxy is presumably the result of merger activity; and we estimate the starburst age to be at least a few times 10(exp 7) yr.
A search for T Tauri stars in high-latitude molecular clouds. 2: The IRAS Faint Source Survey catalog
We present a catalog of infrared point sources from the IRAS Faint Source Survey at Galactic latitudes the absolute magnitude of b is greater than or equal to 30 deg. The aim of this paper is to provide a list of possible star-forming sites at high Galactic latitudes in order to address the question of whether or not the translucent molecular clouds (which are most easily identified at high latitudes) are capable of star formation. The primary list of sources has 12, 25, 60, and 100 micron fluxes within the range typical of pre-main-sequence or T Tauri stars. A secondary list has the same range of 12, 25, and 60 micron fluxes, but only upper limits at 100 microns. A total of 127 candidates from the first category and 65 candidates from the second category are identified and their positions and infrared spectral characteristics tabulated. Although the colors and fluxes of these sources are typical of T Tauri or pre-main-sequence stars and YSOs, extragalactic sources and planetary nebulae sometimes have similar colors. These lists provide a starting point for optical spectroscopy or other techniques to positively identify these objects. We can determine an upper limit to the star forming efficiency of high-latitude molecular clouds assuming all the candidates in our sample are pre-main sequence stars of one solar mass. The upper limit of a few tenths of 1% is less than the star-forming efficiency of local dark cloud complexes such as the Taurus-Auriga or rho Ophiuchus clouds.
Shocked molecular gas around the extremely young source IRAS 03282+3035
We present observations of the shock tracers H2 and SiO around the young stellar object IRAS 03282+3035. This unusual low-luminosity (L approximately = 2 solar luminosity) source drives a strong highly collimated CO outflow, and it is one of the youngest stellar objects known so far. The near-infrared H2 emission, tracing 2000 K gas, comes from extremely high velocity CO bullets along the axis of the blueshifted lobe of the outflow. The millimeter SiO emission, tracing roughly 100 K gas, arises from lower velocity material at the end of the outflow lobe. The lack of high-temperature and high-velocity gas at the end of the outflow lobe indicates there is no not bow shock at the outflow termination. In the context of current jet models this appears to rule out a bow shock driven by a steady state jet. Possible explanations for the structure include a time-dependent jet or a jet dominated by turbulent entrainment.
Star formation in Taurus
Data with the Two Micron All Sky Survey (2MASS) prototype camera were obtained in a 2.3 sq. deg region in Taurus containing Heiles Cloud 2, a region known from Infrared Astronomy Satellite (IRAS) observations to contain a number of very young solar type stars. Data at 1.25 (J), 1.65 (H), and 2.2 (K(sub s)) micrometers are presented. These data are representative of the type and quality of data expected from the planned near-IR surveys, 2MASS and Deep Near-Infrared Survey (DENIS). Near-IR surveys will be useful for determining the large scale variation of extinction with clouds, for determining the luminosity function in nearby clouds down to ranges of 0.1-1.0 solar luminosity, and for finding highly extincted T Tauri stars missed by IRAS because the bulk of their luminosity is emitted shortward of 12 micrometers.
Palomar Prime-Focus Infrared Camera (PFIRCAM)
In a joint effort between engineers and scientists at the Jet Propulsion Laboratory and the California Institute of Technology, a near-infrared (0.8 - 2.6 micrometers) direct imaging system has been developed and integrated into the Caltech Palomar Observatory detector series. The camera system has been tested and operated in a science mode at the prime-focus (f/3.3) of the Hale 5-m Telescope. This paper outlines the system components and performance, including discussion of the detector linearity.
Brackett- Line Emission Maps of Four Galaxies
Observatons of the Br hydrogen recombination line have been made in a sample of four galaxies. The data were acquired with the new Palomar Prime-Focus Infrared Camers (PFIRCAM) mounted at the prime focus (f/3.3) of the Hale 5-m telescope.